Brute Force Time
Estimate the time required to brute-force a password or key given attempt speed.
About Brute Force Time
The total keyspace an attacker must search is charset_size^length. Assuming attempts are tried in random or sequential order, the average time to find the correct password is the time to search half the keyspace, divided by the attacker's guesses-per-second rate. That rate varies enormously by hashing algorithm: fast, unsalted hashes like MD5 can be attempted at tens of billions per second on modern GPUs, while deliberately slow, memory-hard algorithms like bcrypt and Argon2 are designed to make each guess computationally expensive, dropping the achievable rate to thousands or even hundreds per second.
Formulas
Total keyspace
combinations = charset_size ^ length
- C
- Character set size
- L
- Password length
Average crack time
time = (combinations / 2) / hash_rate
- r
- Attacker's hash attempts per second
Worked example
With the default values below, Brute Force Time returns Total Combinations (Keyspace) of 2.183 × 10¹⁴. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Password/Key Lengthaccepts 1–128 characters
- 8 characters
- Character Set Sizeaccepts 2–256
- 62
Results
- Total Combinations (Keyspace)
- 2.183 × 10¹⁴
- Avg. Time — MD5 (50B/s)
- 36.39 minutes
- Avg. Time — SHA-256 (10B/s)
- 3.03 hours
- Avg. Time — bcrypt (50K/s)
- 69.19 years
- Avg. Time — Argon2 (1K/s)
- 3,459 years
Step by step
- 1Values used
- 2Total keyspace
- 3Average crack time
- 4Total Combinations (Keyspace)= 2.183 × 10¹⁴
- 5Avg. Time — MD5 (50B/s)= 36.39 minutes
- 6Avg. Time — SHA-256 (10B/s)= 3.03 hours
- 7Avg. Time — bcrypt (50K/s)= 69.19 years
- 8Avg. Time — Argon2 (1K/s)= 3,459 years
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why use bcrypt or Argon2 instead of MD5/SHA-256 for password storage?
MD5 and SHA-256 are designed to be fast, which is exactly the wrong property for password hashing — it lets attackers try billions of guesses per second on GPUs. bcrypt and Argon2 are intentionally slow and memory-hard, cutting achievable attack rates by 6-7 orders of magnitude.
Why divide the keyspace by 2 for the average time?
If an attacker searches the keyspace in a fixed order (or randomly without repeats), the correct answer is, on average, found after checking half of all possible combinations — not all of them, and not just one.
How much does adding one more character help?
Each additional character multiplies the keyspace by the charset size, so going from length 8 to 9 with a 62-character set multiplies crack time by 62x — length increases have an exponential, not linear, effect on brute-force resistance.
Does this account for smarter attacks like dictionary or rule-based attacks?
No — this models pure brute-force search across the full keyspace. Real-world attacks often succeed much faster using dictionaries, common password lists, and mutation rules that target likely passwords first rather than searching randomly.